Influence of high pressures on CH4, CO2 and H2S solubility in polyethylene: Experimental and molecular simulation approaches for pure gas and gas mixtures. Modelling of the sorption isotherms

• We investigate gas sorption in PE both through experimental and simulation approach.
• Sorption of pure gas and gas mixtures is studied for pressures up to 2000 bar.
• The results obtained from simulation compare favourably to experimental results.
• Different sorption mechanisms are evidenced as a function of the gas nature.
• A model is proposed to describe gas solubility from low to high gas pressure range.

The sorption of methane, carbon dioxide and hydrogen sulphide in polyethylene (PE) was investigated. Data were obtained in a large range of pressures from both experiments and molecular simulation. Monte Carlo (MC) simulations in the osmotic ensemble were used to predict gas concentrations in the amorphous polymer phase. An ad hoc constraint in the osmotic simulations was used to mimic the effect of the crystalline phase. The results obtained from MC simulation compared favourably to experimental results and data from literature. Different sorption mechanisms were evidenced in the low to middle gas pressure range as a function of the gas nature. However, the decrease of gas solubility was evidenced at high pressure. It was assigned to a hydrostatic effect and the bulk modulus of the PE amorphous phase was determined. A simple model allowing the accurate description of gas solubility from low to high gas pressure range was proposed. It was shown to accurately describe the different sorption isotherm shapes obtained for PE and the characteristic parameters of the model were determined for each gas.